Everything You Need to Know about Narcissists, Psychopaths, and Abuse - click on this link: http://www.narcissistic-abuse.com/faq1.html
Subsuming the Object of Envy through Imitation
Some narcissists seek to imitate or even emulate their (ever changing) role models. It is as if by imitating the object of his envy, the narcissist BECOMES that object. So, narcissists are likely to adopt their boss' typical gestures, the vocabulary of a successful politician, the views of an esteemed tycoon, even the countenance and actions of the (fictitious) hero of a movie or a novel.
Destroying the Frustrating Object
Other narcissists "choose" to destroy the object that gives them so much grief by provoking in them feelings of inadequacy and frustration. They display obsessive, blind animosity and engage in compulsive acts of rivalry often at the cost of self-destruction and self-isolation.
Pathological envy is not the same as romantic jealousy. These two emotions have little to do with each other.
Romantic jealousy is a narcissistic defense. It reflects the narcissistic traits and behaviors of possessiveness; objectification (treating the spouse and regarding her as an object); and extension (treating the spouse and regarding her as an extension of oneself: devoid of autonomy, personality, needs, wishes, and emotions). Thus, the spouse's cheating (as in infidelity) is perceived by the narcissist to be tantamount to a violation of and an encroachment on his self.
Exactly like non-narcissists, narcissists are humiliated by having been lied to; suffer abandonment anxiety; compare themselves with the spouse's new paramour; and feel deprived when the "services" of the unfaithful spouse are no longer available to them (a denial of service which may encompass sex, emotional intimacy, house chores, companionship, or any other function.)
Romantic jealousy is the product of a violation of trust (which in the narcissist provokes paranoia: where else lurks deceit?), breach of exclusivity (which threatens the aforementioned narcissistic enmeshment), and denial of possession (which in the narcissist translates to fear of loss and abandonment anxiety.)
Narcissists are, consequently, even romantically jealous of intimate partners their spouse had before the marriage and after the divorce. Some narcissists, realizing that they cannot control their spouses forever, become swingers or engage in group sex, where they feel that, by bringing adultery home, they have "tamed" and "controlled" it. If you can't beat it -- join it, as the saying goes.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)